Related links:

The Comet Nucleus

A comet nucleus is made of a special sort of dust. This theorized dust is called "fluffy" because it could be as light weight and full of holes as a sponge. The holes are filled with frozen gases made of carbon dioxide, carbon monoxide and other gases. Observations of the nuclei of comet Hale-Bopp and Hyakutake have given scientists fresh ideas about comet composition and evolution.

Scientists do not know whether the nucleus is very hard (like solid ground) or very soft and breakable (like a snowball). The Rosetta mission hopes to land a probe on the surface of a comet to find out just how hard it is.

As a comet approaches the Sun, it begins to sublimate, forming the coma and a spectacular tail.
This picture shows that sublimation may happen only in specific places on the nucleus. These spots of evaporation are called "jets". The jets can sometimes help to turn the comet and make it tumble in space. Halley's comet was photographed with three distinct jets on its surface as it approached the Sun in 1986.

You might also be interested in:

This example of Interstellar Dust is a perfect example of the kind of rocky material comet may be made of. The grains themselves seem to be made of smaller grains. There are many holes, or pores. In a...more

Hale-Bopp continues to offer surprises as astronomers study the comet. Using the Hubble Space Telescope and the International Ultraviolet Explorer, astronomers have found that their are distinctly different...more

Comets are disturbed from their orbits in the Oort Cloud and begin a passage into the solar system, spinning and tumbling as they come. The trajectory which they acquire can be hyperbolic, parabolic, or...more

As the ices of the comet nucleus evaporate, they expand rapidly into a large cloud around the central part of the comet. This cloud, called the coma, is the atmosphere of the comet and can extend for millions...more

The image on this page shows the best views we've ever had (so far) of the nucleus of a comet. On January 2, 2004, the Stardust spacecraft flew past Comet Wild 2 at a relative speed of roughly six kilometers...more

We are sad to report that the Comet Nucleus Tour (CONTOUR), which launched July 3, 2002, is currently lost in space. The CONTOUR spacecraft was to explore the nucleus of comets. It was scheduled to fly...more